The present invention relates in general to a fuel filter and a fuel filtering system for use with a vehicle, wherein the fuel filter is located "downstream" from a fuel pump. More specifically, the present invention relates to the design of a fuel filter which is used within a fuel filtering system and which includes a pressure-controlled, spring-biased, internal valve that enables the automatic draining of excess fuel back to either the fuel tank or to a suction-side primary filter. The fuel filter of the present invention includes a water-separation capability such that accumulated water is automatically drained with excess fuel by means of the internal valve, thereby precluding the need for a separate water-drain mechanism. The design of the present invention also precludes the need to prompt the user to activate or open any separate water-drain mechanism in order to periodically drain the accumulated water from the interior of the fuel filter housing.
Fuel filters and fuel filtering systems have been used in the automotive field and related vehicle and equipment fields for a number of years. The structural configurations of these earlier fuel filters and fuel filtering systems have included a number of design variations and improvements, all in an effort to try and solve certain design shortcomings. The present invention is no different in this regard. Certain disadvantages and shortcomings of existing fuel filter and fuel filtering system designs have been considered by the present inventors and the present invention provides structural design improvements in order to overcome and/or improve upon those disadvantages and shortcomings. One concern with fuel filtering systems is whether unfiltered fuel can be delivered to the fuel injectors or other critical engine components which utilize the fuel for combustion. Since small particulate matter can be detrimental to the long term efficacy of the fuel injection equipment (FIE), filtering of the fuel is particularly important for vehicles which use modern, high pressure FIE. When the filtering media cartridge is not installed in the filter housing, it would be an improvement to be able to prevent fuel flow to the FIE. The present invention provides this capability by means of a unique drain passageway which is wide open whenever the filtering media cartridge is removed.
Another concern with fuel filters which have a screw-on or snap-on cap, cover or lid is the entrapment of air inside of the fuel filter housing. As fuel is delivered to the fuel filter, the trapped air can only exit by passing to the engine or injectors or by flowing back to the fuel tank. Since the trapped air is at the top of the fuel volume within the filter housing, its most likely exit path is to flow with the fuel to the FIE and combustion cylinder. Accordingly, trapped air can interfere with the smooth and continuous delivery of fuel to the engine. It would therefore be an improvement to be able to route the trapped air back to the fuel tank. The present invention provides this capability by a unique air vent tube which cooperates with the aforementioned drain passageway.
Another concern with fuel filters and fuel filtering systems which include a water-separation capability is when and how to drain the accumulated water. Since the separated water typically accumulates at the base of the fuel filter housing, below the fuel, the most common approach is to provide a separate water drain valve. Release or activation of the water drain valve can be manual or automatic. With manual draining, the user has to remember to periodically open the drain valve in order to drain the accumulated or collected water. While automatic drain systems are frequently based on the water level and the electronic sensing of that water level, these designs still necessitate a separate drain valve and associated hardware and electronics. These drain systems also involve the addition of hardware, components and electronics outside of the filter housing which can in turn interfere with other engine components.
The fuel which is pumped to the fuel filter is delivered at a flow rate which is greater than the usage rate of the engine. This means that there is excess fuel which has to be returned to a point in the flow loop which is upstream of the fuel filter, such as to the fuel tank or to the fuel pump, for example. The present invention provides a design improvement to this task by incorporating a pressure-regulated drain valve that automatically drains both excess fuel and accumulated water whenever the internal pressure within the filter housing exceeds a predetermined level. This automatic draining of accumulated water precludes the need for any external components, hardware or electronics. The design of the present invention also precludes the need for the user to remember to periodically activate or release the water drain valve.
The improvements of the present invention represent novel and unobvious advances in the state-of-the-art for fuel filters and fuel filtering systems.